Reduction of viscosity of packet



United States Patent REDUCTION OF VISCOSITY OF PACKET PHOTOGRAPHICEMULSIONS John C. McFall and Henry C. Yutzy, Rochester, N. Y., assignorsto Eastman Kodak Company, Rochester, N. Y., a corporation of New JerseyNo Drawing. Application December 16, 1952, Serial No. 326,346

8 Claims. (Cl. 95-7) This invention relates to reducing the viscosity ofpacket photographic emulsions and the use of certain salts in connectiontherewith.

The making of packet emulsions is described and claimed in U. S.application, Serial No. 156,066, now U. S. Patent No. 2,698,794 ofLeopold Godowsky, filed April 15, 1950. In a method described in thatapplication for the making of a packet emulsion a red sensitive emulsionwas prepared and mixed with a cyan coupler, a green sensitive emulsionwas prepared and mixed with a magenta coupler, each emulsion wasseparately incorporated in an aqueous solution of the sodium salt of acopolymer of methacrylic acid and methyl methacrylate following whichthere was then incorporated in each a water soluble salt of a packetforming polymer such as styrenemaleamic acid polymer with resultantpacket formation at this point and these packet emulsions were mixedtogether and coated. In another method described in the Godowskyapplication a packet emulsion was formed of three separate emulsionscontaining couplers corresponding to the sensitivity of the respectiveemulsions, which emulsions were separately mixed with aqueous solutionsof the sodium salt of a copolymer of methacrylic acid and methylmethacrylate (U. S. Patent No. 2,391,181 of Minsk et al.) with aqueoussolutions of water-soluble salts of styrene-maleamic acid polymerwhereupon they were united and coated out on to a support. Packetemulsions are of special value in color photography.

It has been found that with packet emulsions of the type referred to ahigh solution viscosity often is encountered thus presentingdifliculties in coating those emulsions onto a support therefor such asbaryta coated paper or film base which has been supplied with a subbinglayer. In those coating operations should the emulsion be diluted toreduce its viscosity and thereby facilitate the application of thecoating to the support therefor, difficulties arise both in obtainingcoatings of the emulsion of the desired thickness and in the drying ofthe emulsion coating. It has been attempted toreduce the viscosity ofemulsions of this type by a washing operation in which the emulsion ischilled, noodled and washed in cold water but in this procedure it hasbeen found that the volume is increased to a point wherein difficultiesare experienced in the coating operations.

One object of our invention is to provide a method of reducing theviscosity of packet emulsions in which copolymers of methyl methacrylateand methacrylic acid are employed in their preparation. Another objectof our invention is to provide a method for reducing the viscosity ofpacket emulsions in which no undue increase in volume is encountered. Afurther object'of our invention is to prepare packet emulsions in whicha small amount of magnesium nitrate or some other suitable salt has beenincorporated therein. Other objects of our invention will appear herein.

We have found that when packet emulsions of the type described hereinare treated with magnesium nitrate or other suitable water-soluble saltsthat the viscosity of n 2,735,768 Patented Feb. 21, 1956 the emulsion isappreciably lowered with no more than a slight increase in volume. Wehave found that this treatment of packet emulsions with salts mayconveniently be accomplished in either one of two ways:

(1) Noodling the emulsion and bathing the noodles in an aqueous solutionof the salt to be employed, followed by washing the emulsion with water.If desired this method may be carried out by using several successivebaths containing the effective salts accompanied by decanting after eachbath.

(2) Incorporating the salt which is to be used directly into theemulsion without any washing operation.

After the emulsion has been treated in the desired manner either bywashing with a solution of the salt or by incorporating the salt in theemulsion, it may, after dispersing in water to the desired coatingconsistency, be coated onto a support therefor such as a baryta coatedpaper.

The salts which have been found to be most effective for lowering thesolution viscosity of packet emulsions as referred to herein arewater-soluble magnesium, barium and potassium salts such as magnesiumnitrate, potassium nitrate, barium nitrate, barium chloride andpotassium alum. Some of these salts not only improve the viscosity ofthe packet emulsion but also the keeping qualities of the emulsion arebenefited. In the practice of our invention /z--5% of the salt based onthe dry weight of both the gelatin and the resinous material present isadequate to accomplish the desired eifect and by the treatment of thepacket emulsion with a salt of the type described within this range theviscosity of the emulsion is lowered to such an extent that it can bereadily flowed on to a support therefor in the normal coating operation.

In the preparation of packet emulsions of the type described herein inwhich styrene-maleamic acid polymer is used, that polymer may beprepared for instance by reacting together 49 parts of maleamicanhydride and 52 parts of distilled styrene in 1500 parts of dry tolueneusing two parts of benzoyl peroxide to catalyze the polymerization. Themass thus prepared is heated for 2 /2 hours on a steam bath. Uponcooling, the mass is in a form that the solid portion thereof can bewithdrawn. The salt of this polymer may be obtained by adding ammoniumhydroxide thereto, warming to 20-25 C. and filtering off the resultingsolution of the resin salt.

Instead of styrene-maleamic acid polymer other packet-forming polymersmay be employed in preparing packet emulsions the viscosity of which maybe lowered in accordance with our invention. One type of polymer whichhas been found to be useful for packet formation is the styrene-maleicacid type such as obtained by forming an interpolymer of styrene andmaleic anhydride and then treating with ammonia, a primary or secondaryamine or water. Other types are the styrene-acrylic anhydride andstyrene-methacrylic anhydride types. Further disclosure as regards thepolymers suitable for forming packets is contained in the Godowskyapplication Serial No. 156,066 referred to heretofore.

The water-soluble salt of the copolymer of methacrylic acid and methylmethacrylate may be prepared by treating polymers of this type describedin U. S. Patent No. 2,391,181 of Minsk et' al. with a basic'compound inaqueous solution. In order to obtain packet emulsions of excellentcharacteristics photographic emulsions containing a coupler areincorporated in solutions of each of the resins referred to, resultingin packet formation with the resins specified. This, however, has theeffect of increasing the emulsion viscosities making viscosity reductionwith salts in accordance with our invention highly desirable.

The following examples illustrate reducing the viscosities of packetemulsions in accordance with our invention.

Example 1 A green sensitive silver chlorobromide emulsion was preparedcontaining 160 grams of gelatin per mol of silver halide and having atotal weight of 2590 grams per mol of silver halide.

345 grams of magenta coupler 1-(2,4,6 trichlorophenyl)3-[3-(2,4ditertiary amyl phenoxy acetnmido) benzamido] -5-pyraz0lone and 34.5grams of dioctyl hydroquinone were dissolved in 1000 ccs. of normalbutyl phthalate and this solution was added to a mixture of 235 ccs. ofa aqueous solution of sodium isopropyl naphthalene sulfonate and 2040cc. of a 10% aqueous gelatin solution and was dispersed therein forminga magenta coupler dispersion. The total weight of the dispersion wasadjusted with distilled water to 3920 grams. To 9065 grams of the abovesilver halide emulsion there was added 462 milligrams of a greensensitizing dye, 5-[(3-ethyl-2 (3)-a-naphthoxazolylidene) ethylidene] 3n heptyl 1 phenyl 2- thiohydantoin dissolved in 462 cc. of acetone. Themixture was held at 40 for minutes and then 150 ccs. of water plus 3920grams of the above magenta coupler dispersion was added plus 1050 gramsof a 15% aqueous solution of the sodium salt of the copolymer ofmethacrylic acid and methyl methacrylate. The mixture was stirred for /2hour. There was then added to this mixture 1505 ccs. of a 5% aqueoussolution of the ammonium salt of a styrene-maleamic acid polymer and themixture was stirred for 5 minutes. At this point was added an additional3500 ccs. of the 15 solution of the sodium salt of the copolymer ofmethacrylic acid and methyl methacrylate. The mixture was stirredvigorously for 45 minutes at 40 C. and packet formation occurred. Therewas then added 2800 ccs. of a aqueous gelatin solution plus 525 cos. ofan aqueous 10% calcium acetate solution which reacts with the residualstyrene-maleamic acid copolymer in the continuous phase forming theinsoluble calcium salt thereof. The mixture was stirred until thoroughlymixed.

100 grams of the so formed packet emulsion were chilled and noodled.These noodles were bathed for 15 minutes in each of three successivewater baths containing 1% of magnesium nitrate hexahydrate of 200 ccs.each at a temperature of 45 F., the noodles being drained between eachwashing. The weight of the emulsion was increased from 19.3 lbs. to lbs.per mol of silver halide and the final viscosity of 6 cps. was obtained.When the emulsion was diluted to 51.5 lbs. per mol of silver halide theviscosity thereof was 2 cps. as compared with a viscosity of 9 cps. forthe emulsion not treated with magnesium nitrate at this base weight.

Example 2 A packet photographic emulsion was prepared as described inthe preceding example which emulsion was noodled and bathed in 200 ccs.of a 10% solution of Mg(NO3)2.6H2O for 15 minutes at 44 F. The noodleswere then washed in Water for 15 minutes at 47 F. The weight increasedfrom 19.3 lbs. to 26.1 lbs. per mol of silver halide. The viscosity at26.1 lbs. per mol of silver halide was 7 cps. and at 51.5 lbs. per molof silver halide the viscosity of the so treated emulsion was 2.5 cps.as compared with a viscosity of 9 cps. for an emulsion at this weightwhich had not been so treated.

Example 3 A packet emulsion was prepared in the manner described inExample 1. 128 grams of an emulsion of this type was mixed with 15 ccs.of a 10% aqueous Mg(NO3)2.6I-I2O solution and 13 ccs. of water to bringthe silver halide molar weight to 17.2. The viscosity of this emulsionwas 21.5 cps. The emulsion was then diulted to 22.8 lbs. per mol ofsilver halide and the viscosity was 10 cps. A like packet emulsion towhich no salt had been added showed a viscosity at 17.2 lbs. per mol ofsilver halide of 39 cps. and at 22.8 lbs. per mol of silver halide of 18cps.

Example 4 To a packet emulsion of the type described above was added 15ccs. of 10% aqueous KNOs and 13 ccs. of water to bring the silver halidemolar weight to 17.2. The viscosity of the diluted emulsion was 28 cps.at 17.2 lbs. per mol of silver halide whereas an untreated emulsion ofthe same kind at this silver halide molar weight was 39 cps.

Example 5 To 128 grams of a packet emulsion of the same type asdescribed above was added 15 ccs. of 10% aqueous barium nitrate and 13ccs. of water thereby bringing the silver halide molar weight to 17.2.The viscosity was 27.5 cps. The same emulsion but without any treatmentwith salt exhibited a viscosity of 39 cps. at a silver halide molarweight of 17.2.

Although the examples are directed to the treatment of simple packetemulsions, it is to be understood that our invention also applies toemulsions of the mixed packet type such as are described in Examples 15(2-color emulsion) and 16 (3-color emulsion) of U. S. application156,066 of Leopold Godowsky, filed April 15, 1950. In treating emulsionsof the mixed packet type in accordance with our invention the separatecolor sensitive components can each be separately treated with aviscosity reducing salt in accordance with our invention or thedifferent color sensitive components can befirst combined to form themixed packet emulsion and the resulting product may be treated withviscosity reducing salt in accordance with our invention. By thusincorporating the viscosity reducing salt therein the coating of theemulsion thus obtained is facilitated contributing to the ease ofpreparing photographic products from packet emulsions of the typedescribed herein. Our invention is directed to the lowering of theviscosity of packet emulsions in which the water soluble salt of thecopolymer of methacrylic acid and methyl methacrylate is employedparticularly when used with the water soluble salt of a styrene-maleamicacid polymer.

It was found that the emulsions of the packet type which had beentreated with a magnesium, barium or potassium salt as described hereinare readily amenable to coating out onto a support therefor in aconventional coating operation, said coating operation being carried outat high speed and the resulting paper obtained having thereon a uniformcoating of satisfactory thickness in ,contrast to the results obtainedupon coating mixed packet emulsions of like nature and having a similarmolar weight.

We claim:

1. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /z5%, based on the dry weight of gelatinand polymer, of a water-soluble salt selected from the group consistingof the water-soluble inorganic acid salts of magnesium, potassium andbarium.

2. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesbathing the packet emulsion in solid form with an aqueous solution of awater-soluble salt selected from the group consisting of thewater-soluble inorganic acid salts of magnesium, potassium and bariumwhereby /25% of the salt, based on the dry weight of gelatin andpolymer, is imparted to the emulsion.

3. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /2-5% of magnesium nitrate, based on thedry weight of gelatin and polymer.

4. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /z5% of potassium nitrate, based on thedry weight of gelatin and polymer.

5. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /2-5% of barium nitrate, based on the dryweight of gelatin and polymer.

6. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /2--5% of barium chloride, based on thedry weight of gelatin and polymer.

7. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which comprisesadding to the packet emulsion /25% of potassium alum, based on the dryweight of gelatin and polymer.

8. A method for lowering the viscosity of a packet gelatin-silver halidephotographic emulsion containing therein a methacrylic acid-methylmethacrylate polymer and a packet forming polymer selected from thegroup consisting of the styrene-maleamic acid packet forming polymers,the styrene-maleic anhydride packet forming polymers, thestyrene-acrylic anhydride packet forming polymers and thestyrene-methacrylic anhydride packet forming polymers which compriseswetting said emulsion in solid form with an aqueous solution ofmagnesium nitrate so that /25% of magnesium nitrate, based on the dryweight of gelatin and polymer, is imparted to the emulsion.

References Cited in the file of this patent UNITED STATES PATENTS2,565,418 Yackel Aug. 21, 1951 2,607,683 Yackel et al. Aug. 19, 19522,632,704 Lowe et a1. Mar. 24, 1953

1. A METHOD FOR LOWERING THE VISCOSITY OF A PACKET GELATIN-SILVER HALIDEPHOTOGRAPHIC EMULSION CONTAINING THEREIN A METHACRYLIC ACID-METHYLMETHACRYLATE POLYMER AND A PACKET FORMING POLYMER SELECTED FROM THEGROUP CONSISTING OF THE STYRENE-MELEAMIC ACID PACKET FORMING POLYMERS,THE STYRENE-MALEIC ANHYDRIDE PACKET FORMING POLYMERS, THESTYRENE-METHACRYLIC ANHYDRIDE PACKET FORMING POLYMERS AND THESTYRENE-METHACRYLIC ANHYDRIDE PACKET FORMING POLYMERS WHICH COMPRISESADDING TO THE PACKET EMULSION 1/2-5%, BASED ON THE DRY WEIGHT OF GELATINAND POLYMEMR, OF A WATER-SOLUBLE SALT SELECTED FROM THE GROUP CONSISTINGOF THE WATER-SOLUBLE INORGANIC ACID SALTS OF MAGNESIUM, POTASSIUM ANDBARIUM.